Traditionally, 14- and 18-karat gold alloy compositions have been used in the manufacture of various items of jewelry, such as bracelets, necklaces, rings, and the like.
Some gold alloys have been developed that offer the capability of reversibility, by selective application of an appropriate heat treatment, between their annealed-hardness and aged-hardness values. In many cases, there is a considerable difference between these hardness values. Hence, an alloy may be annealed to lower its hardness value. This allows the alloy to be worked more easily. After the alloy has been worked, and the article thereof formed or repaired, the article may be aged-hardened to a higher hardness value to increase its resistance to denting and deformation. However, if there is a subsequent need to rework or repair the item, it may be annealed to reduce its hardness back down to its annealed-hardness value. After the item has been reworked or repaired, it may be aged-hardened to increase its hardness to a higher hardness value. Thus, by selectively heating and cooling these alloy compositions, the hardness of these compositions may be selectively varied. It is known to produce yellow (e.g., U.S. Pats. No. 5,180,551 and 6,676,776), white (e.g., U.S. Pat. No. 5,919,320) and green (e.g., U.S. Pat. No. 6,406,568) alloy compositions having such reversible hardness characteristics.
Grain structure is another characteristic that materially affects the value of an alloy. It has been known to add iridium, cobalt and/or nickel to produce an alloy having a fine grain structure. However, the use of these additives have to be closely controlled for fear of separation of these elements or formation of “hard spots” in the alloy. Nickel is a known cause of an allergic reaction with the skin that results in dermatitis. The use of these various grain refiners is discussed in Ott, “Optimizing Gold Alloys for the Manufacturing Process”, Gold Technology, Issue No. 34 (Spring 2002) [at pp. 37-44].
Other gold alloy compositions are shown and described in U.S. Pat. Nos. 5,173,132 and 5,749,979. The aforesaid articles and each of the aforesaid patents are hereby incorporated by reference.
It would be generally desirable to provide rose-colored gold alloy compositions having hardnesses that are capable of being selectively varied between their respective annealed-hardness and age-hardness values.